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VoLTE and OTT voice applications – what’s the difference?

Posted by Daniel Noworatzky on Jul 5, 2017 3:48:00 PM

When to use VoLTE vs. an OTT voice app

difference between VoLTE and OTT voice apps

In a previous article, we discussed voice over LTE (VoLTE) and its implications for the enterprise VoIP phone system. All voice traffic over the LTE (also known as 4G mobile) network is packetized and conforms to modern VoIP standards, making it the first mobile telephony standard to completely circumvent the traditional circuit-switched telephony infrastructure.

In many ways, VoLTE sounds a lot like over-the-top (OTT) voice applications that leverage the same protocols for voice. In this article, we look at what OTT voice apps are, what VoLTE is in relation to OTT, and the benefits of using one, the other or both over an LTE network.


Over -the-top voice applications over the LTE data network

In general, an OTT app is any application that uses the internet connection of a device (computer, laptop, tablet, smart phone, etc.) to offer a service that is provided by a third party; that is, someone other than the ISP itself. Within the context of an LTE mobile network, an OTT voice app uses the mobile device’s data connection to the internet over the LTE network to offer a voice service by a third party that is independent of the mobile service provider. Several examples of such OTT voice apps include Skype, WhatsApp or Viber. These apps are proprietary clients that are locked into specific voice, video, or instant messaging (IM) services that are accessible worldwide over the internet, provided by the servers of their respective companies. In most cases, free calls can be made between users of these services, and for a small fee, PSTN calls can also be terminated via these services.

Another flavor of voice OTT apps that can be used over an LTE data network is SIP clients. Most mobile smartphone app stores have hundreds of SIP clients available for free download. These are stand-alone apps that use open protocols requiring the provisioning of a SIP server with valid SIP accounts that can be accessed via the LTE data connection. Enterprises often use such a setup in order to extend their internal enterprise telephony network to their mobile employees and partners.

What’s important to note here is that these OTT applications use the mobile telephony network infrastructure only for connectivity to their servers or services via the LTE data connection.


Why is VoLTE not an OTT voice app?

The reason why VoLTE is not classified as an OTT voice app has more to do with the way it is offered rather than the technology itself. This is why it is not classified as such even though its description fits the technical description of an OTT voice app. Unlike the apps described above, VoLTE is almost always a service that is provided by the mobile service provider as an integral part of their service package, rather than by a third party.


What should you use and when?

Different applications and services can be used, depending on the requirements of each business.

Reliability - The integrated VoLTE service offered by the mobile service provider is almost always the most robust voice service that one can have on a mobile telephony device. VoLTE can always automatically fall back on older 3G and 2G network connectivity, providing uninterrupted service even in rural areas where LTE is unavailable.

Reachability and ease of use – VoLTE is always integrated with the PSTN with no usernames or passwords to configure, no apps to download and set up and no servers to provision. The mobile device is reachable from any telephone worldwide with an E.164 format telephone number. If the phone is turned off or out of range, users can be informed of missed calls either with an SMS text message or a voicemail message.

Cost – OTT voice apps such as Skype, WhatsApp and Viber are services that allow free IM, voice and video calls. However, this is only available between registered users of each individual service, and data connectivity is required for these to function.

Convenience and security – OTT voice apps, such as SIP clients, can provide mobile devices with internal short codes (3 or 4 digits for example) as part of the internal corporate dial plan for simple voice connectivity with mobile employees. This solution requires a specifically provisioned and accessible SIP server. This also allows voice conversations to be encrypted using Virtual Private Network (VPN) and security technologies such as IP Security (IPsec).



Although VoLTE resembles an OTT voice app in many ways, it is inherently different in the way it is offered. With the proper combination of VoLTE and OTT voice apps, it is possible to optimally leverage these technologies to customize a solution that suits your specific business needs.

You may also like:

What VoLTE means for the enterprise VoIP system

Why you should connect your VoIP phone system to a mobile network

The benefits of integrating the IoT with your VoIP phone system


Topics: OTT VOIP, Business Telephone System, VoIP, Software Integration, Trends, Mobility, mobile

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